Copper futures were probing fresh contract and five-month highs on Tuesday morning, as fund and chart-based buying extended a recent rally in the face of low metal inventories.
"It was a very strong close yesterday, and I think that spilled over this morning - aggressive investment fund and bank buying," said a New York desk broker.
"When the rest of the market sees that coming in, everyone just bows away, so there are not too many sellers."
At the session highs of $2,900 a tonne on the London Metal Exchange and $1.3440 in New York futures, selling by producers and the trade knocked prices back down again, dealers said.
Benchmark December copper on the New York Mercantile Exchange's COMEX division was up 2.05 cents at $1.34 a lb. at 9:58 am EDT (1358 GMT), in a range of $1.3120 to $1.3440, the highest for futures since April 25. Spot September rose 1.90 cents to $1.3380.